The present invention provides photoiniferters for radical polymerization processes and telechelic polymers made thereby.
In conventional radical polymerization processes, the polymerization terminates when reactive intermediates are destroyed or rendered inactive; radical generation is essentially irreversible. It is difficult to control the molecular weight and the polydispersity (molecular weight distribution) of polymers produced by conventional radical polymerization, and difficult to achieve a highly uniform and well-defined product. It is also often difficult to control radical polymerization processes with the degree of certainty necessary in specialized applications, such as in the preparation of end functional polymers, block copolymers, star (co)polymers, and other novel topologies.
In a controlled radical polymerization process radicals are generated reversibly, and irreversible chain transfer and chain termination are absent. There are four major controlled radical polymerization methodologies: atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT), nitroxide-mediated polymerization (NMP) and iniferters, each method having advantages and disadvantages. The term xe2x80x9ciniferterxe2x80x9d, or xe2x80x9cphotoiniferterxe2x80x9d as it is also known, refers to a chemical compound that has a combined function of being a free radical initiator, transfer agent, and terminator, the term xe2x80x9ciniferterxe2x80x9d being a word formed by the underlined portions of the terms identifying these functions. The photo portion of the term indicates that the polymerization is photolytically induced. This term and its use in the production of block copolymers is well known, particularly because of the work of Takayuki Otsu of the Department of Applied Chemistry, Osaka City University, Osaka, Japan. This work is discussed, for example, in an article by Otsu et al entitled xe2x80x9cLiving Radical Polymerizations in Homogeneous Solution by Using Organic Sulfides as Photoinifertersxe2x80x9d, Polymer Bulletin, 7, 45-50 (1982), an article by Otsu et al entitled xe2x80x9cLiving Mono and Biradical Polymerizations in Homogeneous System Synthesis of AB and ABA Type Block Copolymersxe2x80x9d, Polymer Bulletin, 11, 135-142 (1984), Otsu entitled xe2x80x9cIniferter Concept and Living Radical Polymerizationxe2x80x9d, J. Polymer Science, Pat A, vol. 38, 2121-2136 (2000), and in European Patent Application No. 88303058.7, Publication No. 0 286 376, publication date Oct. 12, 1988.
There is a need for a radical polymerization process which provides (co)polymers having a predictable molecular weight and a narrow molecular weight distribution (low xe2x80x9cpolydispersityxe2x80x9d). A further need is strongly felt for a radical polymerization process which is sufficiently flexible to provide a wide variety of products, but which can be controlled to the degree necessary to provide highly uniform products with a controlled structure (i.e., controllable topology, composition, stereoregularity, etc.). There is further need for a controlled radical polymerization process which provides telechelic (co)polymers capable of entering into further polymerization or functionalization through reactive end-groups, particularly electrophilic end groups.
The present invention provides photoiniferters for controlled radical polymerization processes that comprise compounds of the formula: 
wherein
R1 and R2 are each independently selected from H, an alkyl group, a nitrile group, a cycloalkyl group, a heterocyclic group, an arenyl group and an aryl group, or R1 and R2 taken together with the carbon to which they are attached form a carbocyclic ring;
R3 and R4 are each independently selected from an alkyl group, a cycloalkyl group, an aryl group, an arenyl group, or R3 and R4 taken together with the carbon to which they are attached form a carbocyclic ring;
R5 and R6 are each independently selected from an alkyl group, a cycloalkyl group, an aryl group, an arenyl group, or R5 and R6 taken together with the nitrogen to which they are attached form a heterocyclic ring, R5 and R6 are optionally substituted with phosphate, phosphonate, sulfonate, ester, halogen, nitrile, amide, and hydroxy groups; R5 and R6 may optionally be substituted with one or more caternary heteroatoms, such as oxygen, nitrogen or sulfur;
Q is a linking group selected from a covalent bond, an arenyl group, an aryl group (xe2x80x94CH2xe2x80x94)o, Oxe2x80x94COxe2x80x94Oxe2x80x94(CH2)nxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2CH2O)o-, xe2x80x94COxe2x80x94NR8xe2x80x94CH2)oxe2x80x94, xe2x80x94COxe2x80x94Sxe2x80x94(CH2)oxe2x80x94, where o is 1 to 12, and R8 is H, an alkyl group, a cycloalkyl group, an arenyl group or an aryl group; and
n is 0 or 1.
The present invention also provides photoiniferters that comprise the ring-opened reaction product of the photoiniferters of Formula I and a reactive compound, such as an aliphatic compound, having one or more nucleophilic groups. Such photoiniferters have the general formula: 
wherein
R1 and R2 are each independently selected from H, a nitrile group, an alkyl group, a cycloalkyl group, an arenyl group, a heterocyclic group and an aryl group or R1 and R2 taken together with the carbon to which they are attached form a carbocyclic ring;
R3 and R4 are each independently selected from an alkyl group, a cycloalkyl group, an aryl, an arenyl group, or R3 and R4 taken together with the carbon to which they are attached form a carbocyclic ring;
R5 and R6 are each independently selected from an alkyl group, a cycloalkyl group, an aryl group, an arenyl group, or R5 and R6 taken together with the nitrogen to which they are attached form a heterocyclic ring, R5 and R6 are optionally substituted with phosphate, phosphonate, sulfonate, ester, halogen, nitrile, amide, and hydroxy groups; R5 and R6 may optionally be substituted with one or more caternary heteroatoms, such as oxygen, nitrogen or sulfur;
n is 0 or 1;
Z is O, S or NR8, wherein R8 is H, an alkyl group, a cycloalkyl group, an arenyl group, a heterocyclic group or an aryl group;
R7 is an organic or inorganic moiety and has a valency of m, R7 is the residue of a mono- or polyfunctional compound of the formula R7(ZH)m;
Q is a linking group selected from a covalent bond, an aryl group, an arenyl group, (xe2x80x94CH2xe2x80x94)o, xe2x80x94COxe2x80x94Oxe2x80x94(CH2)nxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94(CH2CH2O)nxe2x80x94, xe2x80x94COxe2x80x94NR8xe2x80x94(CH2)oxe2x80x94, xe2x80x94COxe2x80x94Sxe2x80x94(CH2)oxe2x80x94, where o is 1 to 12, and R8 is H, an alkyl group, a cycloalkyl group, an aryl group, an arenyl group, a heterocyclic group or an aryl group;
m is an integer of at least 1, preferably at least 2.
The photoiniferters of the present invention provide (co)polymers having a predictable molecular weight and a narrow molecular weight distribution. Advantageously, the photoiniferters provide novel multireactive addition polymers having first and second terminal reactive groups that may be used for further functionalization. The present invention further provides a controlled radical polymerization process useful in the preparation of terminal-functionalized (telechelic) (co)polymers, block copolymers, star (co)polymers, graft copolymers, and comb copolymers. The process provides these (co)polymers with controlled topologies and compositions.
The control over molecular weight and functionality obtained in this invention allows one to synthesize numerous materials with many novel topologies for applications in coatings, surface modifications, elastomers, sealants, lubricants, pigments, personal care compositions, composites, inks, adhesives, water treatment materials, hydrogels, imaging materials, telechelic materials and the like.
In another aspect, the invention provides a method for polymerization of one or more olefinically unsaturated monomers comprising addition polymerizing one or more olefinically unsaturated monomers using the photoiniferter comprising the azlactone
It is to be understood that the recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).
It is to be understood that all numbers and fractions thereof are presumed to be modified by the term xe2x80x9cabout.xe2x80x9d
It is to be understood that xe2x80x9caxe2x80x9d as used herein includes both the singular and plural.
The general definitions used herein have the following meanings within the scope of the present invention.
The term xe2x80x9calkylxe2x80x9d refers to straight or branched, cyclic or acyclic hydrocarbon radicals, such as methyl, ethyl, propyl, butyl, octyl, isopropyl, tert-butyl, sec-pentyl, cyclohexyl, and the like. Alkyl groups include, for example, 1 to 18 carbon atoms, preferably 1 to 12 carbon atoms, or most preferably 1 to 6 carbon atoms.
The term xe2x80x9carylxe2x80x9d means the monovalent residue remaining after removal of one hydrogen atom from an aromatic compound which can consist of one ring, two or three fused or catenated rings having 6 to 14 carbon atoms.
The term xe2x80x9carenylxe2x80x9d means the monovalent residue remaining after removal of a hydrogen atom from the alkyl portion of a hydrocarbon containing both alkyl and aryl groups having 6 to 26 atoms, optionally substituted with one or more catenary heteroatoms.
The term xe2x80x9cazlactonexe2x80x9d means 2-oxazolin-5-one groups and 2-oxazolin-6-one groups of Formula I, where n is 0 and I, respectively.
The term xe2x80x9cheterocyclic groupxe2x80x9d or xe2x80x9cheterocyclexe2x80x9d means the monovalent residue remaining after removal of one hydrogen atom from an cycloaliphatic or aromatic compound having one, two or three fused rings having 5 to 12 ring atoms and 1 to 3 heteroatoms selected from S, N, and nonperoxidic O. Useful heterocycles include azlactone, pyrrole, furan, thiophene, imidazole, pyrazole, thiazole, oxazole, pyridine, piperazine, piperidine, and hydrogenated and partially hydrogenated derivatives thereof. The term xe2x80x9cmultifunctionalxe2x80x9d means the presence of more than one of the same functional reactive group; The term xe2x80x9cmultireactivexe2x80x9d means the presence of two or more of two different functional reactive groups;
The term xe2x80x9cpolyfunctionalxe2x80x9d is inclusive of multireactive and multifunctional.
The term xe2x80x9cacid catalystxe2x80x9d or xe2x80x9cacid catalyzedxe2x80x9d means catalysis by a Brxc3x8nsted- or Lewis-acid species;
The term xe2x80x9cmolecular weightxe2x80x9d means number average molecular weight (Mn), unless otherwise specified.
The term (co)polymer refers to homo- and copolymers.
The term (meth)acrylate refers to both methacrylate and acrylate.